Rotary engine rotor

ABSTRACT

A die cast aluminum rotor for a rotary engine wherein the rotor is made with the expendable core process and is formed with a central rib having openings therethrough for internal oil cooling distribution and there are provided hollow rivets which hold covers in place in the rotor side walls to seal the core openings through which the expendable core is supported and also provide communication passages for pressure equalization at the rotor sides.

United States Patent Mitchell 1 Sept. 23, 1975 ROTARY ENGINE ROTOR [75] Inventor: Boris J. Mitchell, Birmingham,

Mich.

[73] Assignee: General Motors Corporation,

Detroit, Mich.

[22] Filed: Sept. 3, 1974 [21] Appl. No.: 502,347

[52] U.S. Cl. 418/61 A; 29/l56.4 R [51] Int. Cl. F02B 53/00 [58] Field of Search 123/801, 8.45; 418/61 A; 29/l56.4 R

[56] References Cited UNITED STATES PATENTS 2,979,042 4/1961 Bentele 123/845 3,489,125 l/l970 Fend 418/61 A X Primary Examiner-C. J. Husar Assistant ExaminerMichael Koczo, Jr. Attorney, Agent, or FirmRonald L. Phillips [57] ABSTRACT A die cast aluminum rotor for a rotary engine wherein the rotor is made with the expendable core process and is formed with a central rib having openings therethrough for internal oil cooling distribution and there are provided hollow rivets which hold covers in place in the rotor side walls to seal the core openings through which the expendable core is supported and also provide communication passages for pressure equalization at the rotor sides.

2 Claims, 6 Drawing Figures US Patent Sept. 23,1975 Sheet 1 of 2 3,907,464

US Patent Sept. 23,1975 Sheet 2 of2 3,907,464

ROTARY ENGINE ROTOR This invention relates to a rotary engine rotor and more particularly to such a rotor made with an expendable core.

In attempting to make a rotary engine rotor of light metal by die casting the rotor in one piece with'aluminum using an expendable core, this core will print into the rotor die and leave unwanted holes in the rotor side walls through which the oil that is normally circulated through the rotor for cooling could exit. According to the present invention these core openings are simply and economically closed by a cover and hollow rivet arrangement. The hollow rivet extends with clearance through an opening in a radially extending central rib in the rotor so as to leave an oil passage about the rivet between the opposite sides of the rib for internal oil circulation and the rivets opposite ends clamp'covers in the core openings to close the side walls. In addition, the opening through the rivet provides a fluid passage between the outboard sides of the rotor side walls to effect side-to-side pressure balance on the rotor.

An object of the present invention is to provide a new and improved rotary engine rotor.

Another object is to provide a rotor for a rotary engine that is cast in one piece with an expendable core with the core openings closed by a cover and rivet arrangement.

Another object is to provide a rotary engine rotor cast in one piece with an expendable core wherein the core openings are closed by a cover and hollow rivet arrangement with the hollow rivet passing with clearance through an opening in a radially extending central rib in the rotor to leave an internal oil passage about the rivet between the opposite sides of the rib and also providing a fluid passage through the rivet between the outboard sides of the rotor to effect side-to-side pressure balance on the rotor.

These and other objects of the present invention will become more apparent with reference to the following drawing and description in which:

FIG. 1 is a side elevational view with parts in section of a rotary engine having a rotor constructed according to the present invention.

FIG. 2 is a view taken along the line 2-2 in FIG. 1.

FIG. 3 is an enlarged view taken along the line 3-3 in FIG. 2.

FIG. 4 is a view taken along the line 44 in FIG. 3.

FIG. 5 is a sectional view showing the die casting of the rotor.

FIG. 6 is a perspective view of the expendable core used to die cast the rotor.

The rotor according to the present invention is for use in a rotary combustion engine of the type shown in FIGS. 1 and 2. In this type engine there is a stationary multi-part outer body or housing 10 having a cavity that is formed by an inwardly facing internal peripheral wall 12 of a rotor housing 14 and a pair of oppositely facing internal end walls 16 of end housings 17. The peripheral wall 12 has the shape of a two-lobe epitrochoid or a curve parallel thereto and a hollow rotor 18 having the general shape of a triangle with three peripheral faces 20 and parallel sides 21 is mounted within the cavity on an eccentric 22 of a crankshaft 23. Crankshaft 23 is mounted on opposite sides of the rotor in sleeve bearing assemblies 24 fixed in the end housings 17 so that it rotates about center line 25 of peripheral wall 14. An annular external tooth stationary phasing gear 26 is integral with the inboard end of the righthand sleeve bearing assembly 24 as viewed in FIG. 1, and is thus fixed to the housing 10. Gear 26 meshes with an internal tooth rotary phasing gear 27 which is formed integral with the right-hand rotor side 21 concentric with the rotor. The meshing gears 27 and 26 have a ratio of 1.5:1 to enforce a fixed, cyclic relation between the rotor and the crankshaft while the rotor faces 20 cooperate with the peripheral wall 12 and end walls 16 to define three variable volume working chambers 28. The chambers 28 are peripherally spaced around the rotor and move therewith with the housing as the rotor rotates about its'axis and planetates with respect to the crankshaft axis to force the crankshaft to rotate three full turns for every single full turn of the rotor with the chambers thus twice undergoing expansion and contraction during each rotor revolution. As shown in FIG. 2, an air-fuel inlet passage 30 whose opening and closing is effected by motion of the rotor provides for periodic admissin of air-fuel mixture to each chamber as it is expanding, a spark plug 31 provides for ignition of the mixture after compression and an exhaust passage 32 whose opening and closing is also effected by motion of the rotor provides for exhaust of the products of combustion from each chamber. Thus, as the rotor rotates in the direction indicated by the arrow, each chamber undergoes intake, compression, expansion and exhaust to provide a power phase for each revolution of the crankshaft.

Sealing of the chambers 28 is provided by a sealing arrangement comprising an apex seal 33 mounted in a slot at each rotor apex, side seals 36 mounted in grooves in each rotor side which extend between the apex seals and an intermediate corner seal 37 mounted in a hole near each rotor apex in each rotor side providing a sealing link between the ends of adjacent side and apex seals. Each of the apex seals 33 is spring biased radially outward to sealingly contact the peripheral wall 12 while both the side seals 36 and corner seals 37 are urged axially outward by springs to engage the opposite end wall 16. In addition to this gas seal arrangement, there is provided a circular oil seal 38 mounted in each rotor side 21 concentric with the rotor which is spring biased axially outward to engage the opposite end wall 16.

The engine is typically lubricated by an oil system comprising a central feed hole 40 in the crankshaft 23 which is supplied with oil under pressure and distributes the oil to radial holes 41 to lubricate the crankshafts main bearings and also to a radial hole 42 to lubricate the rotor bearing, there being provided a separate radial hole 43 to directly lubricate the phasing gears. In addition, oil is delivered to the interior of the hollow rotor 18 from the rotor lubrication hole 42 through holes 46 in the rotor hub with the oil thus delivered to the rotor then flowing out holes 48 to carry away heat and thus cool the rotor.

The details of the engine arrangement thus far described are conventional and it is desirable if the rotor 18 could be readily and economically constructed as a one-piece light weight casting such as by die casting it in aluminum using the well-known expendable core process. However, this casting process would leave openings in the side walls of the rotor which would permit the escape of the oil that is circulated through the rotor for cooling. According to the present invention, this problem is handled in a very simple and economical way which provides an additional beneficial operational feature. Die casting of the rotor in one piece of aluminum using the expendable core process is illustrated in FIGS. 5 and 6. As shown in FIG. 6, the expendable core designated 50 conforms, of course, to the interior desired in the rotor wherein there is to be provided a radially extending central rib 52 which joins the multi-apex peripheral wall 54 of the rotor to the rotors hub 56 to aid the rotor side walls 21 in supporting and distributing the gas load, the side walls 21 also joining the rotors peripheral wall 54 to the hub 56. The expendable core 50 is provided with three pairs of aligned oppositely extending support arms 58 which locate in holes 60 of the two halves 62 of the die as shown in FIG. 5 to support the core in proper position in the closed die. The core 50 is formed to leave openings 66 through the rib 52 radially inwardof each of the rotor apexes to equalize oil cooling distribution inside the rotor and provide further connectioniof the two core portions 68 that are separated by the central rib 52.

The thus cast rotor is left with aligned openings 70 after the core has been removed, i.e. core print-out openings, which are located radially inward of each apex and align with the associated rib opening 66 that provides for internal oil cooling circulation. The core print-out openings 70 are closed by forming an annular recess 72 in the outboard side of the side wall 21 around each of these openings. Then, stamped sheet metal covers 74 conforming to the outline of the recesses 72 are inserted therein. The pairs of covers 74 adjacent each apex are then clamped in place by an elongated hollow tubular rivet 76 which extends through the associated opening 66 in the central rib 52 and through aligned holes 78 provided in the aligned covers 74 and has its opposite ends 80 riveted on the outboard sides of'the covers. As best shown in FIG. 3, substantial clearance is provided between the rivet 76 where it extends through the opening 66 in the rib 52 so as to leave a large external oil passage about the rivet between the opposite sides of the rib to assure fr'ee equalization of oil'cooling distribution within the rotor. Furthermore, the rivet 76 is made hollow so as to provide a communi-' cation passage 82 therethrough between the outboard sides'of the rotor side walls 21 so that during engine operation, pressure equalization on both sides of the rotor is assured between the side seals and oil seals.

The above described embodiment is illustrative of the invention which may be modified within the scope of the appended claims.

I claim:

l. A cast hollow multilobe rotor for a rotary engine having a multi-apex peripheral wall with radially extending side walls, said peripheral wall joined by a radially extending central rib to a center hub, said cast rotor made with an expendable core which leaves aligned openings in said side walls and said rib radially inward of each said apex, said side walls in their outboard sides having a recess around each said opening, a cover mounted in each said recess for closing the associated opening, the covers in aligned openings being in alignment and having aligned rivet holes, and a rivet extending through the aligned rivet holes in each pair of aligned covers and also extending with substantial clearance through the associated opening in said rib for securing the covers to said rotor to close the core openings while leaving an internal oil passage about said rivet between the opposite sides of said rib.

2. A cast hollow multi-lobe rotor for a rotary engine having a multi-apex peripheral wall with radially extending side walls, said peripheral wall joined by a radially extending central rib to a center hub, said cast rotor made with an expendable core which leaves aligned openings in said side walls and said rib radially inward of each said apex, said side walls in their outboard sides having a recess around each said opening, a cover mounted in each said recess for closing the associated opening, the covers in aligned openings being in alignment and having aligned rivet holes, and a hollow rivet extending through the aligned rivet holes in each pair of aligned covers and also extending with substantial clearance through the associated opening in said rib for securing the covers to said rotor to close the core penings while leaving an internal oil passage about said rivet between the opposite sides of said rib and also providing a communication passage through said rivet between the outboard sides of said side walls to effect side-to-side pressure balance on said rotor. 

1. A cast hollow multi-lobe rotor for a rotary engine having a multi-apex peripheral wall with radially extending side walls, said peripheral wall joined by a radially extending central rib to a center hub, said cast rotor made with an expendable core which leaves aligned openings in said side walls and said rib radially inward of each said apex, said side walls in their outboard sides having a recess around each said opening, a cover mounted in each said recess for closing the associated opening, the covers in aligned openings being in alignment and having aligned rivet holes, and a rivet extending through the aligned rivet holes in each pair of aligned covers and also extending with substantial clearance through the associated opening in said rib for securing the covers to said rotor to close the core openings while leaving an internal oil passage about said rivet between the opposite sides of said rib.
 2. A cast hollow multi-lobe rotor for a rotary engine having a multi-apex peripheral wall with radially extending side walls, said peripheral wall joined by a radially extending central rib to a center hub, said cast rotor made with an expendable core which leaves aligned openings in said side walls and said rib radially inward of each said apex, said side walls in their outboard sides having a recess around each said opening, a cover mounted in each said recess for closing the associated opening, the covers in aligned openings being in alignment and having aligned rivet holes, and a hollow rivet extending through the aligned rivet holes in each pair of aligned covers and also extending with substantial clearance through the associated opening in said rib for securing the covers to said rotor to close the core penings while leaving an internal oil passage about said rivet between the opposite sides of said rib and also providing a communication passage through said rivet between the outboard sides of said side walls to effect side-to-side pressure balance on said rotor. 